1. Field of the Invention
The invention relates to the testing of electronic components.
When they come off the production line, semiconductor electronic components are tested by a testing machine when they are still joined together on a wafer and/or in the state of unit components, packaged or not packaged, possibly in the form of strips.
The testing machine comprises electrodes laid out respectively so as to come into contact with the conductive zones (or regions) of the components. Signals are applied to these electrodes and picked up by them by means of an interface configured by testing means of the machine.
The testing machine comprises a set of electronic modules and software programs whose general function is to compare each measured value with a reference value or interval (or field of validity), in order to make a general decision on whether the component is sound or defective. Finer decisions may be taken, for example when similar components are manufactured together but guaranteed with different tolerance brackets.
More specifically, the software programs may be broken down into a library of tools, a definition of constants, variables and data tables (multiplets) especially for the reference intervals, a sequence of elementary tests for the acquisition of measurements and their comparison with the reference intervals and a final decision mechanism.
The elementary tests of the sequence are stored in a memory of the testing means and subdivided into steps managed by a sequencer. Thus, each test generally comprises the following steps:
a) configuring the interface with a view to the performance of a chosen elementary test (this step consists of the selective designation of the electrodes to which the chosen electrical signals must be applied), PA1 b) after the application of the electrical signal (or signals) chosen for the elementary test, waiting for a first nominal fixed stabilizing period (or at least the longest of the first stabilizing periods) corresponding to the test, PA1 c) selectively picking up, on the designated electrodes, the electrical measurable quantity or quantities designated by the elementary test and representing the responses of the component to the chosen electrical signals, PA1 d) if necessary, waiting for a second fixed measurement period (or at least the longest of the second measurement periods) corresponding to the elementary test in order that the measurement of the designated electrical quantity may be stabilized in the measurement machine, PA1 e) reading the measurement or measurements of the electrical quantity or quantities designated by the elementary test, and PA1 f) comparing the measured electrical quantity with the domain of validity corresponding to the elementary test. PA1 electrodes of these components are subjected, at an initial date, to electrical potentials, PA1 a measurement is made, at a measuring date, of the values of the potentials set up at the terminals of these components, and PA1 these measured values are compared with typical values in order to accept or reject the components as a function of this comparison, PA1 a nominal statistical image is determined at a nominal date corresponding to a nominal waiting duration after this initial date, for an acceptable batch of components and for a given test, PA1 an intermediate statistical image is determined for this acceptable batch at least one intermediate date prior to or after the end of the nominal waiting duration, PA1 the earliest possible intermediate date during the measurement duration is chosen by the comparison, using a criterion, of the nominal and intermediate statistical images of the measured values, and PA1 the earliest possible intermediate date is chosen as the date of measurement of the test.
2. Description of the Related Art
Since the number of test operations to be performed is generally very great, the overall wait that results from the adding together of the first and possibly the second waiting phases (or periods) is great (each waiting phase may last at least some milliseconds). This is a major problem in an industry that is constantly seeking higher productivity.
The wait is further aggravated by the fact that the duration of each elementary waiting phase of a testing operation is fixed rather on the higher side, for quality is still more important than productivity. This precaution makes it possible to cover the entire range of variations between the batches.